Publications by authors named "Rajendar Dyapa"

3 Publications

  • Page 1 of 1

Dehydrative glycosylation with cyclic phosphonium anhydrides.

Org Biomol Chem 2016 Dec;15(1):51-55

Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.

Cyclic phosphonium anhydrides generated from bis-phosphine oxides and trifluoromethanesulfonic anhydride are shown as general coupling reagents in a dehydrative glycosylation reaction of C1-hemiacetals. This reaction protocol is characterized by a broad substrate scope and high yields, including reactions of O-, C-, N-, and S-based nucleophiles with furanose, pyranose, and deoxysugar donors.
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http://dx.doi.org/10.1039/c6ob01812bDOI Listing
December 2016

Formal Synthesis of (+)-Lasubine II and (-)-Subcosine II via Organocatalytic Michael Addition of a Ketone to an α-Nitrostyrene.

Org Lett 2015 Nov 22;17(21):5312-5. Epub 2015 Oct 22.

Department of Chemistry, Memorial University , St. John's, Newfoundland, Canada A1B 3X7.

The first examples of an organocatalytic Michael addition of a ketone to in situ generated α-nitrostyrenes are reported. A suitably functionalized γ-nitroketone obtained from the organocatalyzed Michael addition was converted into (+)-2-epi-lasubine II, the immediate synthetic precursor of (+)-lasubine II and (-)-subcosine II (enantiomers of the natural quinolizidine alkaloids). Two of the three stereocenters in (+)-2-epi-lasubine II are set by the Michael reaction.
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http://dx.doi.org/10.1021/acs.orglett.5b02677DOI Listing
November 2015

Enantioselective approach to functionalized quinolizidines: synthesis of (+)-julandine and (+)-cryptopleurine.

Org Biomol Chem 2012 Sep 20;10(33):6776-84. Epub 2012 Jul 20.

Department of Chemistry, Memorial University, St. John's, Newfoundland, Canada.

An efficient synthesis of functionalized quinolizidines was developed from an enantiomerically enriched γ-nitroketone, which is easily prepared by an organocatalytic ketone-nitroalkene Michael addition. Oxidative ring expansion of the nitroketone followed by reductive ring-opening leads to a suitably functionalized nitrodiol which is an intermediate to the title compounds.
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http://dx.doi.org/10.1039/c2ob25689dDOI Listing
September 2012